P. aeruginosa was originally a kind of bacterium having low pathogenecity; however, as a result of the proliferative replacement of bacteria due to the general administration of antibiotic drugs, infectious diseases arising from drug resistant P. aeruginosa have recently been increasing in immunodeficient patients, especially those with cystic fibrosis, diffuse panbronchiolitis (DPB), thermal burns, and cancer and the patients are often found falling in a serious condition. For treating a patient with P. aeruginosa infectious disease properly, early diagnosis is of imperative necessity, and such diagnosis requires a monoclonal antibody which can detect P. aeruginosa rightly, which further requires an antigen specific to P. aeruginosa for preparing said antibody. The development of P. aeruginosa antigen which has high immunogenecity with less side effects and can be used as a vaccine for humans and animals, for instance, a mink, against P. aeruginosa infections is also desired. Furthermore, in the treatment of P. aeruginosa infections there is a problem that the use of antibiotic drugs are not always sufficiently effications because there are many cases where P. aeruginosa is drug resistant and some cases where the patient suffers from a weakened immune response. Research has accordingly been conducted concerning the immunotherapy by use of anti-P. aeruginosa antibodies, especially its monoclonal antibodies, but no methods have yet been developed to such an extent as to be clinically useful.
As the surface antigens of P. aeruginosa, lipopolysaccharide (LPS), outer membrane protein (OMP), flagella, pili, and polysaccharide arising from the slime are known. Of these surface antigens, LPS has a polysaccharide O side chain which determines the serotype of P. aeruginosa and there are 16 kinds of serotypes (according to Homma's classification) ranging from 1 to 16 known presently. LPS also has a core region and lipid A besides the O side chain. Lipid A is buried inside the outer membrane of P. aeruginosa, from which the core region extends outside the outer membrane through 2-keto-3-deoxyoctonate and the O side chain extends from the core region further outside. It is known that an antibody to LPS can be readily produced in humans and animals and has protective potencies against infections. There are, however, problems that this O side chain of LPS has the serotype specificity and that LPS itself is poisonous to the living body.
Attempts have been made to obtain a polysaccharide chain antigen having high immunogenecity with no toxicity from LPS of P. aeruginosa. Japanese Patent Laid-Open Publication No.175440/'84, for instance, describes that a polysaccharide antigen with a molecular weight of 5,000 to 40,000 having no endotoxin activity can be obtained by removing lipid A from LPS of P. aeruginosa by treatment with acetic acid. This type of antigen has polysaccharide O side chain and accordingly still retains the serotype specificity.
Japanese Patent Laid-Open Publication No.29622/'84 discloses that a hybridoma, which is deemed to recognize O side chain and produce monoclonal anti-P. aeruginosa mouse antibody, is obtained by cloning a hybridoma (fused cell) which is prepared by fusion of spleen cells of a BALB/C mouse immunized with LPS of P. aeruginosa (antibody producing cells) with mouse myeloma cells (P3-X63-Ag8-U1 strain).
The antibody to O side chain of LPS offers a problem of having its scope of application limited depending upon the object of therapy and diagnosis because of the serotype specificity. It is more advantageous and safe to use anti-P. aeruginosa human antibody of the homogeneous protein for therapy of or making a diagnosis of human diseases, and this raises the necessity of establishing a mouse-human hybridoma or a human-human hybridoma by use of antibody producing human cells. Different from the case of animals, however, the case of using human cells involves another problem of difficulty in the collection and treatment of appropriate antibody producing cells since it is not possible to adopt a method in which men are immunized with a large amount of P. aeruginosa or their surface antigens and then effectively stimulated antibody producing cells are collected and used for cell fusion, and accordingly, no report has yet been made as to definitely successful cases.